1. Field of the Art
The present invention relates to a flexible disk drive and, more particularly, to a manual loading mechanism for a magnetic disk drive which has a pair of magnetic heads for recording and reproducing information out of a magnetic recording medium making contact with, respectively, the upper and lower surfaces of the recording medium.
2. Description of the Prior Art
A flexible disk drive is used to record information in and read information from a floppy disk or a flexible disk which is loaded in the disk drive. A disk drive of the type using a floppy disk which accommodates information on both surfaces thereof, i.e. a two-sided floppy disk, is provided with a pair of magnetic heads. A floppy disk is rotated while chucked by a hub or a spindle that is held in driven connection with a spindle motor. The magnetic heads are mounted one above the other and operated such that when the floppy disk is loaded, the upper one of the heads, or upper head, is lowered toward the lower one, or lower head, so as to hold the disk between the heads. The heads are movable in the radial direction of the disk to record information or read information from a desired track of the disk.
A prerequisite with a flexible disk drive of this kind is that magnetic heads surely make contact with a magnetic recording medium, e.g. a two-sided floppy disk. This is implemented with an arrangement wherein an upper head assembly which holds a magnetic head adapted for the upper surface of a recording medium is movable downward toward a carrier which holds a magnetic head adapted for the lower surface of the medium.
A flexible disk drive is known in the art which uses a solenoid for raising and lowering a magnetic head as stated above. However, a problem with a solenoid type head loading mechanism is that it adds to the overall weight, cost and power consumption of the apparatus due to the great number of constituent parts required, e.g. a solenoid, a drive circuit and a power source. Another problem is that when the power of the apparatus is switched off while a recording medium is loaded, the medium cannot be ejected and should it be ejected forcibly, it might damage the magnetic head. On the other hand, when the recording medium is removed slowly, the upper and lower heads are brought into close contact with each other because the apparatus is still in a loaded condition. When the apparatus is switched on again with the two heads held in contact, a cam mechanism of the apparatus is actuated in a direction for raising the upper head resulting that a gimbal which supports the head, is deformed to impair the head.
In the light of the above, there has been proposed a head loading mechanism which replaces the solenoid with a cam mechanism for raising and lowering the upper head, as disclosed in Japanese Patent Laid-Open Publication No. 2268/1984. In such disclosed mechanism, a lug extends sideways from an upper head so that, when a cam type bar slides, it moves the upper head up and down through the lug.
While a magnetic recording medium is not loaded in the apparatus, the carrier and the upper head are spaced from each other to prevent the magnetic heads from interfering with each other. The flexible disk drive is provided with a head protection mechanism in order to implement such actions which are associated with the carrier and upper head.
An example of prior art disk protection devices is disclosed in Japanese Patent Laid-Open Publication No. 98361/1984, entitled "Media Protection Device for Floppy Disk Drive." The protection device disclosed is such that as a floppy disk is inserted into a disk drive, a clamp lock is angularly moved by the disk to in turn allow an operating lever to be rotated by hand. As the operating lever is manually rotated, a collet adapted to press the center of the disk is lowered toward the hub of a spindle motor, causing the upper head to move downward toward the lower head. So long as a floppy disk is not inserted, the clamp lock is maintained in its original or inoperative position to inhibit the rotation of the operating lever. Under this condition, the upper and lower heads are spaced from each other, and so are the collet and the hub.
The above-described type of prior art protection device suffers from various drawbacks, as will be described. Because an inlet for a recording medium which is formed in the disk drive is not provided with a closure member or door, and, therefore, is open all the time, dust particles are apt to enter the disk drive to reach the gap between the hub and the collet and become deposited on the surfaces of the heads. Such would lower the chucking force acting on the medium and/or render the recording and reading of data incomplete or impracticable. Further, it is impossible for a recording medium to be effectively freed from undulation, or waving, inside of the disk drive.
Meanwhile, there has been proposed a flexible disk drive of the type having a door adapted to close an opening for the ingress/egress of a floppy disk. This type of disk drive is constructed such that alignment of the center of a floppy disk with that of a hub, chucking of the disk, and access of a magnetic head to the disk are effected by being interlocked with a closing motion of the door. Specifically, while the door is moved toward a position for closing the opening, an upper head makes access to a floppy disk to hold it in cooperation with a lower head and, at this instant, a collet is about to start aligning the center of the disk with that of the hub. Stated another way, the access of the upper head to the floppy disk is completed before the collet centers the disk, thus, exerting an excessive load on the subsequent centering action. This sometimes prevents the collet from performing accurate centering and, thereby, brings about an occurrence that the edge of the center hole of a floppy disk is partly caught between the outer periphery of the collet and the inner periphery of the hub. When the disk is chucked in an eccentric position due to such inaccurate alignment, data write-in or read-out becomes incomplete or impractical and, in the worst case, valuable information stored in the disk is destroyed.
The above occurrence may be eliminated by another known structure which uses a solenoid or like drive source. Specifically, after the collet has centered a floppy disk with respect to the hub, the collet and the hub chuck the disk and, at the same time, the solenoid is energized to cause the upper head to make access to the disk. Such a scheme, however, has a problem which is inherent in a solenoid type drive. Namely, the solenoid not only increases the overall weight of the disk drive but also has to be accompanied by a drive circuit for operating the solenoid in the above sequence and a power source for the drive circuit, resulting in increases in cost and power consumption.